1. Field of the Invention
The present invention is related to a process of reductively dehalogenating halo-organic substances in solid or liquid form. During this process the substance or mixture of substances is treated by adding elementary alkali metal, alkaline earths, aluminium or iron as the reducing agent and at least one reagent with relatively easily activated hydrogen to provide the source of hydrogen. This process is especially suitable not only for the detoxification of halo-organically contaminated solids and other materials with complex compounds, but also the decontamination and if required the recycling of liquid or predominantly liquid substances which have been halo-organically contaminated.
2. Description of Related Art
Until now it has not been possible to detoxify toxic polyhalogenated organic contaminants with any of the cleaning techniques or technology currently available in ways which have been either economically or ecologically advantageous or had future potential. These substances are frequently present as contaminants, and what is more in large quantities, in the ground, in sediment on riverbeds or on the seabed, in sludge, in the dust particles collected in filters, in building materials, in oil which has seeped out, in used oil, etc which means that they have come in contact with and are found in the company of an indeterminate number of foreign substances with a great range of different characteristics. The decontamination and cleaning up of such a complex combination of heterogeneous, solid, solid-liquid or liquid materials and old dump sites poses particularly difficult problems.
It is true that there are a number of thermal processes and other very energy-intensive processes for destroying dangerous hydrocarbons of the sort named above and also for those which in particular are dispersed throughout materials of a complex composition. Included here, among others, are incineration at a high temperature and incineration in baths of molten glass or in salt baths. However, each of these processes presents some specific disadvantages so that there is a need to develop alternative technologies.
For example, incineration at a high temperature is not only extremely cost-intensive, but also creates new problems. In polychlorinated compounds it can cause PCDD (dioxins)/PCDF (dibenzofuranes) to be formed which must be removed afterwards using several involved processes from the flue gas and from the dust particles collected in the filters, then disposed of. The currently used method of xe2x80x9cdisposalxe2x80x9d of these highly toxic dust particles frequently consists of dumping them in so-called hazardous waste dumps.
Of the biological methods of breaking down toxic organic compounds in complex matrices, each also presents its own specific disadvantages which restrict the ability to make general use of them.
Processes based on the use of alkali metals have found a certain acceptance. In these processes, pulverised metal suspensions or metal dispersions are used in indifferent liquid mediums, like for example white oil; however, the range of their applications is mainly restricted to a few specific problems, ie. the detoxification of relatively pure liquid contaminants or mixtures of contaminants or practically homogeneous, contaminated liquids which do not contain water, such as, for example, transformer oil or used motor oil containing PCBs.
Further processes, in which other non-noble metals alone are used with a low power of reduction, like for example aluminium, zinc or iron, are not suitable for the detoxification of certain groups of important materials, for example polychlorinated aromatics, because the latter cannot be fully dechlorinated with these metals. Not all chlorine atoms of a polychlorinated molecule are removed in this way and detoxification is not achieved, or only in the presence of toxic catalysts or promoters, for example, triphenylphosphine, nickel or nickel compounds which for toxicological reasons also cause serious problems. The use of toxic substances for the dehalogenation of halo-organic substances in soil, sediment, etc only means exchanging the existing type of contamination for another one and thus does not offer a solution to the problem.
The known processes which are used for liquids or mixtures of liquids cannot easily be transferred to solids. It is frequently difficult for reagents to reach halo-organic substances which are contained in solids due to the high level of resistance to transport in reactions between solids. Polyhalogenated organic substances are present in the environment as contaminants, for example, in the soil, in the sediment on riverbeds or on the seabed, in sludge, in the dust particles collected in filters, in building materials or in oil which has seeped out, thus without exception in very heterogeneous solid or solid-liquid materials. These polyhalogenated organic substances can be found in large quantities and due to the complex forms and conditions that these matrices can be present in and as a result the various ways they can be resistant to transport they are particularly difficult to get at and thus they can only be made to react partially or not at all.
Thus, the problem which is the basis of this invention consists of creating a process for reductively dehalogenating halo-organic substances in such a way that it is possible to dehalogenate, using a universally applicable process, various heterogeneous solid and liquid mixtures of substances, in particular also mixtures of a complex composition and contaminated areas of ground in which not all of the substances present are known. This process should neutralise as many of the contaminants as possible and not give rise to any new harmful by-products.
In addition, the process should be as simple as possible to carry out and take effect relatively quickly.
To solve this problem according to the invention, the idea is to use a process as described at the beginning and then subject the halo-organic material or the mixture of substances to milling or grinding with mechanical activation with all substances present being treated together in one step and being reductively dehalogenated more or less completely.
The invention can be applied to halo-organic compounds which are contained in foreign substances or mixtures of foreign substances in solid or liquid form, and also to solid or liquid halo-organic substances, whether present in their pure form or mixed in with other halo-organic substances. When using the basic process, these substances or mixtures of substances are treated in one single step only, in which all the components are mixed together intensively, along with at least one reducing agent and one source of hydrogen, with the reaction taking place in mild operating conditions.